As the term is broadly defined by marketeers, marketing involves all aspects of interaction with the customer and encompasses product design, promotions, pricing, distribution and many aspects of business planning.

Unfortunately, the vast majority of marketing advice and materials available
today are not aimed at startup ventures. They are aimed at corporations
with established product lines, somewhat established brands and some marketing
budget.
The first rule of marketing in a technology startup is this:
don’t spend any money. The second rule: don’t hire someone that
wants to spend money. The third
rule:
hire someone that knows how to spend someone else’s money. You
need to keep as much of your cash as possible to build out your
product—if it really has the potential to change the world, the
press and analysts will get excited and you’ll get valuable
coverage without spending huge budgets on advertising.

However, you do need to generate awareness and recognition,
stake your position in the market and start generating momentum
as quickly as possible. You need a head of marketing to lead
these efforts. Unfortunately these can be the most expensive
people you’ll ever hire.